1. FIELD OF THE INVENTION
The present invention relates to medical devices implanted within the human body. The instant invention pertains to device systems being implanted within the human body for draining cerebrospinal fluid during the treatment of hydrocephallus. The subject invention pertains to an improved cerebrospinal fluid draining system including a check valve mechanism which allows passage of cerebrospinal fluid in one direction. The instant invention relates to a cerebrospinal fluid draining system having a check valve where the opening and closing of the check valve is formed about a fulcrum.
2. PRIOR ART
Systems for draining cerebrospinal fluid are known in the art. The closest prior art known to the inventors of the subject cerebrospinal fluid draining system in U.S. Pat. No. 3,566,875 of which this invention is an improvement. In this prior art system, a slit is utilized for the outlet passage from the check valve. However, upon experimentation it has been found that the dimensions of the slit are important in the control of the fluid egressing from the check valve. In the prior art draining system the slit is formed throughout substantially the elongated length of the check valve. The slit extended into the arcuate dome contour of the check valve mechanism. After experimentation it has been found that when the slit forming the outlet passage extends into the arcuate region of the substantially cylindrical dome shaped check valve, that control of the opening of the slit is diminished. Further, the slit defining the outlet passage did not reliably close when the pressure differential between and upstream area and a downstream area dropped below a predetermined level.
Additionally, the system shown in U.S. Pat. No. 3,566,875 was found to be deficient in the total closing of the outlet passage. Such prior systems did not allow for repeated total closing of the outlet passage due to the fact that there was not return closing forces applied to the check valve mechanism. This had the deleterious effect of permitting continual draining of the cerebrospinal fluid even when the pressure differential between the upstream and downstream areas was less than a predetermined amount.